System and method for machine-to-machine application based congestion control

ABSTRACT

A method and apparatus for reporting events in a machine-to-machine environment are provided. Upon detection of an event, a determination is made whether to report the event with or without a delay. If the event is to be reported with a delay, then reporting is delayed for a period of time. If an event notification is received prior to the expiration of the delay period, then the reporting of the event may be canceled as event has already been reported by another element. If not, then another determination is made whether to report the event with or without another delay. This process continues until either the event has been reported or an event notification corresponding to the event has been received from another element.

This application claims the benefit of U.S. Provisional Application Ser.No. 61/407,301, filed on Oct. 27, 2010, entitled “Machine-to-MachineApplication Based Congestion Control Scheme,” which application ishereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to a communications systems andmethods, and, in particular embodiments, to a machine-to-machineapplication based congestion control scheme.

BACKGROUND

Machine-to-Machine (M2M) service refers to technologies that allowcommunication between devices (wireless or wired) through an accessnetwork, or between a device and a server that may be carried outwithout any human interaction. For example, M2M uses a device (such as asensor or meter) to capture an event (such as temperature, inventorylevel, etc.), which is relayed through a network (wireless, wired orhybrid) to an application (software program) that translates thecaptured event into meaningful information (for example, items need tobe restocked). Such communication was originally accomplished by havinga remote network of machines relay information back to a central hub foranalysis, which would then be rerouted into a system like a personalcomputer.

Modern M2M communication has expanded beyond a one-to-one connection andchanged into a system of networks that transmits data to personalappliances. The expansion of wireless networks across the world has madeit far easier for M2M communication to take place has lessened theamount of power and time necessary for information to be communicatedbetween machines.

With support for M2M devices, however, there can be order of magnitudeincrease in number of devices supported by the network. While themajority of M2M devices may only report small amounts of datainfrequently, the large numbers of M2M devices, such as Smart Meters(SMs), give rise to potential “traffic burst” scenarios that arise whenlarge numbers of M2M devices report or react to a common event, such asa large number of SMs reporting a power outage, a large number ofsensors reporting an earthquake, and the like. Regardless of thetriggering event, such scenarios may lead to a large number of M2Mdevices simultaneously or near simultaneously trying to access thesystem to report the same event, thereby possibly degrading networkperformance.

SUMMARY

The embodiments of the present disclosure provide a system and a methodfor a machine-to-machine application based congestion control scheme.

In an embodiment, a method is provided, wherein the method comprisesdetecting an event, determining whether to queue reporting of the event,and if it is determined to queue the event, waiting for a time period.After the time period expires, the determining is repeated.

In another embodiment, a method comprising: detecting an event anddetermining a random number is provided. The random number is used todetermine a time period to delay. After delaying, a determinationwhether an event notification has been received is made, and if not, anevent report corresponding to the event is sent.

In yet another embodiment, a system is provided. The system comprises anevent detector to detect an occurrence of an event and a random numbergenerator coupled to the event detector, the random number generatorproviding a random number. A comparator is coupled to the random numbergenerator, such that the comparator determines whether the providedrandom number is above a threshold. An event report transmitter iscoupled to the comparator, such that the event report transmitter sendsan event report corresponding to the event, and a delay unit is coupledto the comparator to delay further processing of the event for a timeperiod. A notification receiver is coupled to the delay unit to receivean event notification from another system, the event notificationcorresponding to the event.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a model of a network that can utilize aspects of thepresent disclosure;

FIG. 2 is a flow chart illustrating steps in a first embodiment;

FIG. 3 is a flow chart illustrating steps in a first embodiment;

FIG. 4 is a block diagram of a system of an embodiment the presentdisclosure; and

FIG. 5 is a block diagram of one example to implement embodiments of thepresent disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments are discussed in details below.It should be appreciated, however, that the present disclosure providesmany applicable inventive concepts that can be embodied in a widevariety of specific contexts. The specific embodiments discussed aremerely illustrative of specific ways to make and use the invention, anddo not limit the scope of the invention.

In one aspect, the present disclosure provides a new application layerbased congestion control scheme. Embodiments avoid or reducetransmission of redundant non-critical information by staggering of theinformation transmitted by the M2M devices. In addition, the M2M devicecan discard the queued information once it determines that theinformation is no longer needed.

In one embodiment, the system provides an application layer basedcongestion control scheme. This embodiment scheme may proactively avoidtransmission of redundant non-critical information by staggering theinformation generated by the M2M devices. In addition, the M2M devicemay discard the queued information once it determines that theinformation is no longer pertinent, for example, when it is detectedthat another M2M device has already transmitted the information.

FIG. 1 illustrates a simplified example of a network 100 that canutilize aspects of the present disclosure. A mobile station (MS) 102,which may represent an M2M device communicating via a wirelesstransmission protocol, is in communication with a base station (BS) 104.While only one MS 102 and BS 104 are shown, it is understood that alarge number of devices can be in communication simultaneously. The basestation 104 in turn communicates with an edge gateway or router 106, forexample, via a GRE (generic routing encapsulation) tunnel. The edgegateway/router 106 is coupled to the core network 108. Communicationscan be transferred via this network to an enterprise back office 110 orwhatever other destination is intended for the communications.

As noted above, the large numbers of M2M devices, such as Smart Meters(SMs), give rise to potential “traffic burst” scenarios that arise whenlarge numbers of devices report or react to a common event. To deal withthis congestion (for example, eliminate unnecessary traffic and allowonly emergency related calls to proceed) some wireless technologiesincorporate some means of access prioritization over the air byspecifying Access Classes (AC). A device is assigned one or more AC andthe network limits access attempts by broadcasting a barred Access Classlist. If the device AC is a member of the barred Access Class list, thedevice may not attempt to connect to the network. Upon detection ofcongestion or a priori knowledge of a potential traffic burst trigger,the network can suitably update the barred Access Class list to abatethe congestion.

One drawback with this AC approach is that the network may not be awareor may not react in time to the network congestion and cannot update thebarred Access Class list in time. This implies that the large numbers ofM2M devices will continue to attempt to access the network andcontribute to the overload condition. Embodiments such as thosediscussed herein may reduce or prevent this problem by staggeringtransmission of the information by the M2M devices (e.g., SMs, MSs, orthe like), thereby reducing transmission of redundant, non-criticalinformation. In addition, the M2M device may discard the queuedinformation if it determines that the information is no longerpertinent.

It should be noted that FIG. 1 illustrates a wireless network system forillustrative purposes only. In other embodiments, the M2M devicescommunicate via a wired communications system. Furthermore, the networkmay comprise both wireless M2M devices and wired M2M devices.

FIG. 2 illustrates a process for controlling reporting of events inaccordance with an embodiment. Generally, the process avoidstransmission of redundant non-critical information by staggeringtransmission of the event reporting by the M2M device. In addition, theM2M device may discard the event report that have yet to be reported bythe M2M device if it is determined that the event report is no longerpertinent, such as may be the case if the event has already beenreported by another device in the network.

Referring first to step 202, an event is detected. The event may be, forexample, a power outage, inclement weather, an earthquake, hardwarefailure, software failure, or any number of other events that theknowledge of an occurrence of the event is desirable to another networkdevice. It should be noted that these examples are provided forillustrative purposes only and are not meant to limit the claims.

Upon detection of an event in step 202, processing proceeds to step 204,wherein it is determined whether or not the event is a shared event or alocal event. Shared events are events that may be reported by two ormore M2M devices remotely located. For example, a power outage,inclement weather, or an earthquake may affect a large area and, hence,may affect multiple M2M devices over a large area. Other events may belocal in that the event affects a particular M2M device or a relativelyfew number of M2M devices that are located within a region. For example,a local event may include a faulty battery backup, low disk storage,and/or the like that may affect a single M2M device. In another example,a local event may be a house fire that may be reported by two or moreM2M devices located within or near the house.

Because local events are typically reported only by that particular M2Mdevice, and hence may not unnecessarily burden the network, upondetermining in step 204 that the event is a local event, processingproceeds to step 206, wherein an event report corresponding to the localevent is transmitted (wired, wirelessly, or hybrid). It should be notedthat the events may be system level events, region specific, device typespecific, application specific, a combination of those, etc.

If, on the other hand, a determination is made that the event is ashared event (e.g., events that may be detected by multiple M2Mdevices), processing proceeds to steps 208-216, wherein the duplicationof reporting of shared events by each affected M2M device may be reducedor prevented. Initially, in steps 208 and 210 a decision is made whetherto delay reporting of the event (with probability 1-p) or to report theevent without a delay (with probability p). In an embodiment, such asthat illustrated in FIG. 2, the decision comprises comparing a randomnumber to a threshold. For example, step 208 illustrates generating arandom number between, for example, 0 and 1. The random number may bedetermined by any suitable technique, such as being based on a systemclock, thermal characteristics, noise levels, movement, and the like. Itis understood that a random number includes a pseudo-random number.

In step 210, the random number is compared to a threshold orprobability. In this embodiment, if the random number is less than thethreshold, then processing proceeds to step 206 wherein an event reportcorresponding to the event is transmitted without any further backoffdelay. Otherwise, processing proceeds to step 212 wherein a backoffdelay is performed. In this example embodiment the random numbergenerates numbers that are uniformly distributed on the interval [0, 1].Because the random number, theoretically or practically, has an equalprobability of being equal to all values between 0 and 1, the thresholdrepresents a probability that the random number is below or above thethreshold. For example, a threshold of 0.5 represents an equalprobability that the event will be reported and that reporting of theevent will be delayed. Similarly, a threshold of 0.3 represents a 30%probability that the event will be reported without any further backoffdelay and 70% probability that reporting of the event by this particularM2M device will be delayed.

The threshold or probability may be the same for all events, or may bespecific to the event, or may be specific to the type or category ofevents. The threshold or probability may also be based upon the numberof devices that share the event. For example, an event that is shared bymany devices may have a threshold set lower than an event shared by onlya few devices. The threshold or probability may also be based upon thecriticality of the event. For example, if an event is considered acritical event, then the threshold may be set high, thereby increasingthe likelihood that the event will be reported sooner even though it mayresult in an increase in network traffic. Conversely, a non-criticalevent may have a lower threshold, thereby increasing the probabilitythat the event report will be delayed. Furthermore, the probabilitiesfor each event or type of event may be individually controlled and theprobabilities for each M2M device may be individually controlled.Furthermore, the threshold or probability may be adjusted based upon theresult of the transmission, e.g., how many times the transmission hasbeen delayed. In an embodiment, it may be desirable to allow the updateand control of the probabilities via a network interface, therebyallowing the probabilities to be set from a remote device, such as acentrally located system administrator.

In step 212, the system waits for a backoff delay period. Similar to theprobabilities, the backoff delay may be a global/default delay period ormay be specified for individual events or types of events. The backoffdelay may also be adjusted based upon the result of transmission, e.g.,how many times the transmission has been delayed. Generally, the backoffdelay period delays reporting of the event, waiting to see if anotherdevice, such as another M2M device, reports the event. Accordingly, theM2M device continues to monitor communications to listen for an eventnotification corresponding to the event to be reported. The value of thebackoff delay may be a predetermined value, randomly generated,determined by a network command, or the like. This allows criticalshared events, such as an external security alarm detecting a neighbor'scar/burglar alarm and alerting E-911, to be given a shorter backoffdelay as compared to a non-critical shared or local event.

In step 214, a determination is made whether or not an eventnotification corresponding to the event has been received from anotherdevice, such as another M2M device, a base station, a server, an M2Mserver, or the like. The event notification may be sent by the otherdevice using any suitable protocol, including unicast, multicast, andbroadcast messaging. If a determination is made that an eventnotification corresponding to the event has been received, then there isno need to report the event and the queued event report is discarded asillustrated in step 216.

In another embodiment, a network command may be sent instead of or inaddition to the event notification to cause the M2M device to cancelreporting of the event. The network command may be, for example, to setthe threshold or probability to 0, which would signal the M2M devicethat the event report is not to be sent. Other network commands, such asan explicit message to cancel the reporting, may also be used. In anembodiment, the command to set the probability to 0 may be included inthe event notification message received from another device, such asanother M2M device, a base station, a server, an M2M server, or thelike, and may be sent using any suitable protocol, including unicast,multicast, and broadcast messaging.

The event report and/or event notification may be a specific message ora broadcasted message. Some communications systems, such as WiMAXsupport application layer based broadcasting/multicasting. In systemssuch as these, the event report/notification messages, as well asprobability commands, backoff delay commands and/or the like, may becommunicated to the M2M devices via a unicast, multicast, and/or abroadcast message.

Otherwise, if a determination is made that an event notificationcorresponding to the event has not been received by the expiration ofthe backoff delay period, then processing returns to step 208.

It should be noted that the method provided above is but one example ofan embodiment for illustrative purposes to demonstrate the concepts andthat other embodiments may utilize a different process. For example, inanother embodiment, a determination of whether an event is a sharedevent or a local event step 204 may be combined with steps 208 and 210.As discussed above, each event or category of event may have its ownprobability or threshold. Local events may be given a probability orthreshold of 1, thereby indicating the local event is to be reportedwithout delay. An example of a local high priority event might be that ahouse is on fire and the system should not wait for neighbors to detectand notify the authorities. In this case, if the event for a house fireis given a probability of 1, then that event would be reportedimmediately without a backoff delay.

FIG. 3 illustrates a process for controlling reporting of events inaccordance with another embodiment. The process begins in step 302,wherein an event is detected. Upon detecting an event, processingproceeds to step 303, wherein a determination is made whether the eventis a shared event. As discussed above, shared events are events that maybe reported by two or more M2M devices remotely located, and localevents are events that affect a particular M2M device or a relativelyfew number of M2M devices located within a region. Because local eventswill be reported only by that particular M2M device, or a relatively fewM2M devices, and hence does not unnecessarily burden the network, upondetermining in step 303 that the event is a local event, processingproceeds to step 312, wherein an event report corresponding to the localevent is transmitted (wired, wirelessly, or hybrid).

If, on the other hand, a determination is made that the event is ashared event (e.g., events that may be detected by multiple M2Mdevices), processing proceeds to step 304 and a random number isgenerated. In contrast to the embodiment discussed above with referenceto FIG. 2 in which a uniform distribution is used for the random numbergenerator, in this embodiment it may be desirable to utilize a randomnumber generator that utilizes a non-uniform distribution. For example,in an embodiment, the random number is generated according to acumulative distribution function (CDF), which may be configured orderived from given parameters such as the threshold values used in theprevious embodiment. In this manner, the probability is greater nearzero than farther from zero. However, this embodiment may utilize auniform distribution, or other distribution, for the random numbergenerator.

In step 306, the system waits for a backoff delay. In this embodiment,the backoff delay is determined based upon the random number generatedin step 304. For example, the random number generated in step 304 mayrepresent a number of a predetermined unit of time that the system is towait or such number of time units may be calculated from the randomnumber. The predetermined unit of time may be, for example,microseconds, seconds, frames, multiples thereof, or the like. Forexample, in an embodiment, a CDF may be derived from the thresholdvalues p used in the previous embodiment resulting inF(t)=1−(1−p)^(t+1), where t is the number of delay intervals to queuethe event report. This embodiment may first generate a random number xusing a random number generator that generates numbers that areuniformly distributed over the interval [0,1). The random number x maythen be used to compute

$t = {\lfloor \frac{\ln( {1 - x} )}{\ln( {1 - p} )} \rfloor.}$

After the expiration of the backoff delay, processing proceeds to step308, wherein a determination is made whether an event notificationcorresponding to the event has been received. If an event notificationcorresponding to the event has been received, than the correspondingevent report is discarded, as indicated in step 310. Otherwise, theevent report is transmitted as indicated in step 312.

FIG. 4 is a simplified block diagram of an apparatus 400 that mayincorporates embodiments of the present disclosure. Referring to thisfigure, an event detector 402 communicates with a random numbergenerator 404, which in turn communicates with a comparator 406, whichcommunicates with a queue/delay unit 408. A notification receiver 401communicates with the queue/delay unit 408 and the random numbergenerator 404 to operate as described above. An event indicationtransmitter 412 communicates with the event detector 402 and to thecomparator 406.

This system can be used to perform the method described with respect toFIGS. 2 and 3. It should be noted, however, that depending on theparticular embodiment, the connections between the components may vary.For example, as indicated by the dashed lines in FIG. 4, the comparator406 may not be used and the random number generator 404 may communicatewith the queue/delay unit 408. This may be applicable for the embodimentdiscussed above with reference to FIG. 3, wherein a backoff delay isbased upon the random number. As discussed above, in this embodiment,there is no need to compare the random number to a threshold orprobability.

FIG. 5 illustrates a processing system that can be utilized to implementmethods of the present disclosure such as those discussed above. In thiscase, the main processing is performed in a processor 502, which can bea microprocessor, digital signal processor or any other appropriateprocessing device. Program code (e.g., the code implementing the methodsdisclosed above) and data can be stored in a memory 504 or any othernon-transitory storage medium. The memory 504 can be local memory suchas DRAM or mass storage such as a hard drive, optical drive or otherstorage (which may be local or remote). While the memory 504 isillustrated functionally with a single block, it is understood that oneor more hardware blocks can be used to implement this function.

In one embodiment, the processor 502 can be used to implement the blocksshown in FIG. 4. For example, the processor 502 can serve as a specificfunctional unit at different times to implement the subtasks involved inperforming the techniques of an embodiment. Alternatively, differenthardware blocks (e.g., the same as or different than the processor) canbe used to perform different functions. In other embodiments, somesubtasks are performed by the processor while others are performed usinga separate circuitry.

FIG. 5 also illustrates an I/O port 506, which can be used to providethe data to and from the processor 502. In the case of a wireless (e.g.,mobile) device, the I/O port 506 can be coupled to an antenna. In thecase of a wired device, the I/O port 506 can be connected to a networkinterface.

A sensor 508 is also illustrated in FIG. 5. This block is provided toillustrate the source of the event being detected. This can be any typeof sensor or other detector, whether operated automatically or manuallyor both.

Embodiments such as those discussed above may reduce network traffic,particularly during specific events that may cause a high burst rate oftraffic, such as a power outage. This is achieved by, among otherthings, providing proactive congestion handling by delaying thereporting of the event in some of the devices.

Embodiments such as those disclosed herein are applicable to manydifferent transmission technologies. For example, embodiments may beutilized in IEEE 802.11, ZigBee, or the like wireless/wired systems. Asknown, IEEE 802.11 is a set of standards carrying out wireless localarea network (WLAN) computer communication in the 2.4, 3.6 and 5 GHzfrequency bands, and ZigBee is a specification for a suite of high levelcommunication protocols using small, low-power digital radios based onthe IEEE 802.15.4-2003 standard for Low-Rate Wireless Personal AreaNetworks (LR-WPANs), such as wireless light switches with lamps,electrical meters with in-home-displays, consumer electronics equipmentvia short-range radio. While these systems may not explicitly provide anAC congestion control mechanism, embodiments such as those disclosedherein may nevertheless provide congestion control. It should be noted,however, that embodiments such as those disclosed herein may be used inconjunction with a transmission technology's AC congestion controlmechanism.

It should also be appreciated that flexibility in parameter (e.g.,random number, threshold, backoff delay) selection allows one to “tune”the network to suit a particular application, event, and/or network.Further, flexibility in parameter selection allows support for theprioritization of alarms/urgent traffic. Parameters may beassigned/changed by the system or the device.

Implementation of embodiments of the invention can reduce traffic innetwork by throttling traffic in the host. Even in the absence ofcongestion (or detection by network), the algorithm allows for reductionof redundant traffic transmission over the air interface. Embodimentsprovide more sensitive/rapid reaction to congestion since they do nothave to wait for the network to detect congestion and send updatedbarred access list.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method comprising: detecting an event;determining whether the event is local or shared, wherein the eventbeing shared comprises the event being a large scale power outage,inclement weather, or a combination thereof; when the event is local,reporting the event without queuing; when the event is shared,determining whether to queue reporting of the event, wherein determiningwhether to queue reporting of the event comprises generating a randomnumber and determining whether the random number indicates to queuereporting of the event; and upon determining to queue reporting of theevent, waiting for a time period and repeating the determining.
 2. Themethod of claim 1, further comprising reporting the event upondetermining not to queue reporting of the event.
 3. The method of claim1, further comprising receiving a notification during the time periodthat the event has been reported.
 4. The method of claim 3, furthercomprising canceling reporting of the event after the receiving thenotification that the event has been reported.
 5. The method of claim 1,further comprising repeating the waiting after the repeating thedetermining.
 6. The method of claim 1, wherein the event being localcomprises the event affecting only a single device.
 7. The method ofclaim 1, further comprising randomly generating the time period.
 8. Themethod of claim 1, further comprising determining the time period inaccordance with how many times a reporting of the event has beendelayed.
 9. A method comprising: detecting an event; determining whetherthe event is local or shared, wherein the event being shared comprisesthe event being a lame scale power outage, inclement weather, or acombination thereof; when the event is local, reporting the eventwithout waiting; and when the event is shared, (a) determining a randomnumber, wherein the random number is based at least in part on acumulative distribution function (CDF); (b) waiting a time period, thetime period being based at least in part on the random number; (c) afterthe waiting, determining whether an event notification has beenreceived; and (d) upon determining the event notification has not beenreceived, sending an event report corresponding to the event.
 10. Themethod of claim 9, wherein the event being local comprises the eventaffecting only devices in a single building.
 11. The method of claim 9,wherein the random number has a non-uniform distribution.
 12. The methodof claim 9, wherein the random number represents a number of time unitsto delay.
 13. The method of claim 12, wherein the time units are frames.14. A system comprising: an event detector configured to detect anoccurrence of an event and to determine whether the event is local orshared; a random number generator coupled to the event detector, andconfigured to generate a random number when the event is shared; acomparator coupled to the random number generator, the comparatorconfigured to compare the random number with a threshold; an eventreport transmitter coupled to the comparator, the event reporttransmitter configured to send an event report of the event when theevent is local, or when the random number is less than the threshold; adelay unit coupled to the comparator and configured to delay furtherprocessing of the event for a time period when the random number isabove the threshold; and a notification receiver coupled to the delayunit and configured to receive an event notification from anothersystem, the event notification corresponding to the event, wherein therandom number generator is coupled to the notification receiver andconfigured to generate another random number upon being notified by thenotification receiver that the event notification corresponding to theevent has not been received from another system.
 15. The system of claim14, wherein the comparator is configured to select the threshold basedupon a category of the event.